1. Field of the Invention
The present invention relates to abdominal impedance measurement apparatuses for human bodies.
2. Description of Related Art
In order for accurate measurements to be taken of areas of visceral fat and subcutaneous fat in the bodies of humans, body fat determination apparatuses have been used that calculate body fat data on the basis of tomographic images obtained by various CT (computed tomography) procedures, including X-ray CT and impedance CT, or by MRI (magnetic resonance imaging).
Conventionally, studies have been made in which indexes of body fat were calculated on the basis of impedances measured using impedance measuring electrodes that were brought into contact with the abdomen of a human subject. For example, according to one study, the mass or area of visceral fat of a human body is calculated on the basis of impedance measured using a pair of current-supplying electrodes in contact with the anterior and posterior surfaces of the abdomen and voltage-measurement electrodes in contact with the flanks of the abdomen, and on the basis of the waist circumference. The calculation method was obtained from correlations among the results of CTs, impedances, and the waist circumferences, as disclosed in Development of Visceral-fat Measuring Method Using Abdominal Bioelectrical Impedance, by Miwa R Y O, Himan Kenkyu (Journal of Japan Society for the Study of Obesity), Japan, Japan Society for the Study of Obesity, 2003, Vol. 9, No. 2, pp. 32-38.
There has also been a study in which impedance measurement electrodes are mounted on a belt that is wound around the abdomen of a human subject, whereby the impedance measurement electrodes are brought into contact with the anterior surface of the abdomen, and the subcutaneous fat mass is estimated from the measured abdominal impedance, as disclosed in Assessing abdominal fatness with local bioimpedance analysis: Basics and experimental findings), by Hermann SCHARFETTER et al., (found in an online search on Feb. 15, 2007), URL: http://www.imt.tugraz.at/scharfetter/no_sync/publications/scharfetter_IJO—01.pdf#search=‘herma nn%20scharfetter%20assessing%20abdominal’
and in JP-A-11-113870.
In the measurement of bioimpedance in humans, even for one particular human subject, the measured results may vary depending on the positions of the measurement electrodes. Therefore, in order to ensure the reproducibility of measurements, the measurement electrodes should always be placed at the same locations. For example, it is possible to consider the transverse plane that passes through the navel of a human subject and is vertical to the median line to be the reference plane relative to which the measurement electrodes should always be arranged.
However, it is difficult, in practice, to arrange impedance measurement electrodes at such reference positions. For example, in the method in which a belt on which impedance measurement electrodes are arranged is wound around the abdomen, there is a possibility that the positions of the measurement electrodes may be out of alignment due to deformation of the belt. Furthermore, when the human subject is, for example, a bedridden disabled person or an elderly bedridden person, winding the belt around the abdomen requires a great deal of care.
JP-A-2005-288023 discloses, in FIG. 14, an apparatus for measuring impedance in which voltage-measurement electrodes are mounted on a fixed support and current-supplying electrodes are mounted on pivotable flaps. The electrodes are pressed onto the anterior surface of the abdomen of a human subject.
However, since the technique in JP-A-2005-288023 necessitates the pressing of the electrodes onto the anterior surface of the abdomen of a human subject, the measured results of impedance may vary depending on the strength of the pressing. The pivotable flaps on which the current-supplying electrodes are mounted are pivotable relative to the fixed support, but the pivot-angle of each flap with respect to the fixed support is manually adjusted and cannot be set constant even for a single human subject. The measured results of impedance may vary depending on the pivot-angle. Therefore, the same reproducibility of measurements is not always achieved.